Using the Mail task in Apache Ant

Since the Ant task reported:

Failed to initialise MIME mail: javax/mail/MessagingException

I decided to download the mail.jar and activation.jar from Sun's website and copy those two jar files in the lib directory of Apache Ant in order to make sending attachments using MIME work and bypassing the default mail handling of the Mail task in Apache Ant. 
And indeed, after downloading javamail-1_3_3_01.zip (which contains mail.jar), jaf-1_0_2-upd2.zip (which contains activation.jar), and copying the two jar files into the lib directory of Apache Ant, the Mail task no longer complained, and Mozilla Thunderbird was able to understand that the new mail it received had indeed attachments. 
Apache Ant and MIME mail related
 - contains mail.jar 
 - contains activation.jar 
 - Apache Ant manual